IB/ipath: Support for SerDes portion of IBA7220

The control and initialization of the SerDes blocks of the IBA7220 is
sufficiently complex to merit a separate file.
Signed-off-by: NMichael Albaugh <Michael.Albaugh@qlogic.com>
Signed-off-by: NRoland Dreier <rolandd@cisco.com>